A Comparison of Shallow Water Model Results for Three Estimates of a Composite El Niño Forcing

Abstract

A linear shallow water model on an equatorial ?-plane is driven by three different estimates of the heating rate perturbation during seven seasons of a composite El Niño episode. In two cases the heating perturbations for this model are assumed to be closely linked to the pattern of sea surface temperature anomalies. In the, third the heating is related to direct estimates of precipitation departures. The model-derived winds based upon these three estimates are compared to one another and to data available from marine weather reports. An analysis of area averaged winds, surface latent heat fluxes and moisture convergences shows general agreement with observations over the composite El Niño seasons for the results of all three forcing estimates, although the model results using the direct precipitation estimates seem generally to be the poorest. A second analysis explores the similarity of smaller-scale features of the model results to the observations. This suggests that the simple parameterized heating using sea surface temperature estimates gives the only solutions which fairly well identify smaller-scale, variations.